Process of cold rolling steel sheets



United States Patent PROCESS OF COLD ROLLING STEEL SHEETS Jesse Donnelly, Hamilton, Ontario, Canada, assignor to Wallace McClung Donnelly, Hamilton, Ontario, Canada No Drawing. Application August 28, 1952 Serial No. 306,953

1 Claim. (Cl. 80-60) This invention relates to cold rolling of steel sheets, and more particularly to cold rolling of steel sheets to light gauges.

In the cold rolling of steel sheets to light gauges, various types of oils and fats are used as a lubricant. A film of the lubricant is left on the sheet after it has been cold rolled. It is well known that when using the present day lubricants, the sheets have a rather porous and comparatively coarse surface after rolling into which the lubricant is forced by the extreme pressures exerted in the rolling operation. The lubricant may become trapped in the interstices of the porous surface and may become carbonized in any subsequent annealing of the sheet.

It is accordingly the main object of the invention to provide a lubricant that will burn off a rolled sheet without leaving any residue and which is of such consistency and character as to enable the satisfactory rolling of the sheet to a light gauge such as, for example, .0082 inch.

It is another object of the invention to provide a method of lubricating a steel sheet during cold rolling whereby the resulting rolled sheet will present an unpitted smooth surface.

It isa further object of the invention to employ a lubricant for a steel sheet during cold rolling which is available as a cheap by-product.

I have discovered and satisfactorily tested, and conclusively proved, that the present-day step or operation of passing the cold rolled sheet through a hot alkaline bath when the sheet is to be galvanized can be dispensed with by using a high free fatty oil having a fatty acid content not greatly under 50% but not much over 75%, the balance of the oil content being a neutral oil in which a small amount of glyceride is present. Such an oil not only does away with the necessity of passing the cold rolled sheet through a hot alkaline bath, but smokes off in the annealing furnace, leaving a sheet clean for either galvanizing or tinning. Furthermore, by the use of a lubricant having the composition referred to, the surface finish of the steel is neither porous nor coarse grained, but presents a compact close-grained surface; therefore, the lubricant is not driven deeply into the surface, and this condition facilitates a thorough burning off of the lubricant in the subsequent annealling furnace treatment. Similarly the use of such a lubricant renders possible the satisfactory cold rolling of sheets for tinning.

Such an oil is obtainable as acidulated vegetable oil foots. As is known, in the caustic refining of vegetable oil as in the manufacture of vegetable shortening and oleo-margarine, the free fatty acids are refined out of the oils into a residue which includes a small 2,896,486. Patented July 28, 1959 amount of neutral oil. The residue is then acidulated as by sulphuric acid to neutralize the caustic, and is known as refined acidulated vegetable oil foots. Such acidulated vegetable oil foots have a high free fatty acid content of about 50% to and a relatively small amount of glyceride in about the order of 9 to 10% the remainder being substantially water as is Well known. The refined acidulated vegetable oil fonts are preferably filtered before they are used in order to remove any fibre debris.

The highly satisfactory properties of this oil are attributable to its high free fatty acid content. The free fatty acids, containing no glyceride, are burned 01f at the high temperature of the annealling furnace, the neutral oil, in which glyceride is present, provides lubrication, and is burnt off in the furnace.

The oil can be applied or caused to be applied as such to the sheet, or as a water emulsion in which the water is kept at a temperature of between and F. It imparts to the cold rolled steel sheet a better reductibility and stretch and a brighter finish, while requiring possibly less, but certainly no more screwdown and motor load than are required by the use of the present-day rolling oils in which natural fatty acid oils or fats are used.

Free fatty acids have an afiinity for water and remain in solution or emulsion with a minimum amount of agitation and no chemical or additive of a soluble oil is necessary where a closed circuit re-circulating system is in use. Such fatty acid oils have a viscosity of 43 seconds as against 57-59 seconds of most fatty acid oils.

Such refined acidulated vegetable oil foots, because they are a by-product, can be procured at a very low cost. Their use as a lubricant in cold rolling thus renders possible the utilization of a product which because of the little, if any, demand for it, is for all practical purposes a waste material. The cost of cold rolling is thus appreciably reduced.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

In the method of processing steel sheets to light gauges, the steps comprising: cold rolling each sheet; and during rolling, applying acidulated vegetable oil foots obtained in the caustic refining of vegetable oils as in the manufacture of vegetable shortening and margarine and consisting of between about fifty percent and seventyfive percent free fatty acid, about ten percent neutral oil and the remainder substantially water, to surfaces of the sheet being rolled to form a non-carbonizing lubricating film thereon achieving a close grained rolled finish for said sheet.

References Cited in the file of this patent UNITED STATES PATENTS 1,819,764 Blecker Aug. 18, 1931 1,918,207 Grobstein et al. July 11, 1933 1,936,583 Clapp Nov. 28, 1933 1,948,194 Williams Feb. 20, 1934 2,310,563 Wilke et al Feb. 9, 1943 2,345,199 Hodson Mar. 28, 1944 2,510,379 Christenson June 6, 1950 2,529,191 Rocchini Nov. 7, 1950 2,632,734 Nunn Mar. 24, 1953 FOREIGN PATENTS 506.474 Great Britain May 30, 1939 

